Fluid analysis system with densitometer having electrically isolated vibrating tube

ABSTRACT

A vibrating-tube fluid measurement device includes a tube, a base block, a magnet which applies a magnetic field to the tube, an excitation source which generates vibration of the tube, a vibration sensor which measures a signal corresponding to a vibration frequency of the tube, and an electrical isolator formed of glass, wherein the vibrating tube is mounted to a base block via the electrical isolator and electrically isolated from the base block via the electrical isolator.

BACKGROUND

The oil and gas industry has developed various tools capable ofdetermining formation fluid properties. For example, borehole fluidsampling and testing tools such as Schlumberger's Modular FormationDynamics Testing (MDT) Tool can provide important information on thetype and properties of reservoir fluids in addition to providingmeasurements of reservoir pressure, permeability, and mobility. Thesetools may perform measurements of the fluid properties downhole, usingsensor modules on board the tools. These tools can also withdraw fluidsamples from the reservoir that can be collected in bottles and broughtto the surface for analysis. The collected samples are routinely sent tofluid properties laboratories for analysis of physical properties thatinclude, among other things, oil viscosity, gas-oil ratio, mass densityor API gravity, molecular composition, H₂S, asphaltenes, resins, andvarious other impurity concentrations.

The reservoir fluid may break phase in the reservoir itself duringproduction. For example, one zone of the reservoir may contain oil withdissolved gas. During production, the reservoir pressure may drop to theextent that the bubble point pressure is reached, allowing gas to emergefrom the oil, causing production concerns. Knowledge of this bubblepoint pressure may be helpful when designing production strategies.

Characterizing a fluid in a laboratory utilizes an arsenal of devices,procedures, trained personnel, and laboratory space. Successfullycharacterizing a fluid in a wellbore uses methods, apparatus, andsystems configured to perform similarly with less space and personalattention and to survive in conditions that quickly destroy traditionallab equipment. Identifying the undesired phase change properties of afluid is especially useful when managing a hydrocarbon reservoir.

SUMMARY

In accordance with example embodiments, a device for measuring aproperty of a fluid sample includes: a tube configured to receive thefluid sample; a base block; a magnet; an excitation source configured togenerate vibration of the tube when the fluid sample is received in thetube such that a circulation of an electrical current along a portion ofthe tube is subjected to at least one magnetic field produced by themagnet; a vibration sensor configured to measure a signal correspondingto a vibration frequency of the tube, the vibration frequency varying asa function of, e.g., the density of the fluid sample; and an electricalisolator comprised of glass, wherein the tube is hermetically sealed tothe base block via the electrical isolator and electrically isolatedfrom the base block via the electrical isolator.

In accordance with example embodiments, a system for characterizing afluid includes: a phase transition cell configured to receive the fluid;a piston configured to control pressure of the fluid; a pressure gaugeconfigured to measure the pressure of the fluid and to provideinformation to control the piston; and a densitometer configured tomeasure density of the fluid. The densitometer includes: a tubeconfigured to receive a fluid sample; a base block; a magnet; anexcitation source configured to generate vibration of the tube when thefluid sample is received in the tube such that a circulation of anelectrical current along a portion of the tube is subjected to at leastone magnetic field produced by a magnet; a vibration sensor configuredto measure a signal corresponding to vibrations of the tube, and anelectrical isolator comprised of glass, wherein the tube is mounted tothe base block via the electrical isolator and electrically isolatedfrom the base block via the electrical isolator.

In accordance with example embodiments, a method includes: placing adoped glass material in a base block; inserting a hollow tube into thedoped glass material; heating the doped glass material to a temperatureat which the doped glass material melts; allowing the doped glassmaterial to cool to form a solid glass isolator that mechanicallysupports the hollow tube with respect to the base block and electricallyisolates the hollow tube from the base block.

Further features and aspects of example embodiments of the presentinvention are described in more detail below with reference to theappended Figures.

FIGURES

FIG. 1 shows a wireline logging system at a well site in accordance withone embodiment of the present disclosure;

FIG. 2 shows a wireline tool in accordance with one embodiment of thepresent disclosure;

FIG. 3A shows a fluid analyzer module in accordance with one embodimentof the present disclosure;

FIG. 3B shows a fluid analyzer module in accordance with anotherembodiment of the present disclosure;

FIG. 4A shows a portion of a vibrating-tube densitometer.

FIG. 4B shows a top view of the structure of FIG. 4A.

FIG. 4C shows a cross-sectional view corresponding to section A-A ofFIG. 4B.

FIG. 4D shows an enlarged partial sectional view corresponding tosection B of FIG. 4C.

FIG. 5A shows a portion of a vibrating-tube densitometer.

FIG. 5B shows an exploded view of the structure of FIG. 5A.

FIG. 5C shows a cross-sectional view of the structure of FIG. 5A.

FIG. 5D shows a partial sectional view corresponding to section C ofFIG. 5C.

FIG. 5E shows a subassembly incorporating the structure of FIG. 5A.

FIG. 5F shows an assembly incorporating the subassembly of FIG. 5E.

FIG. 5G shows the structure of FIG. 5A with an electrical control systemand electrode leads in place.

FIG. 5H shows the structure of FIG. 5A with an electrical control systemand an optical detection system.

DESCRIPTION

At the outset, it should be noted that in the development of any suchactual embodiment, numerous implementation-specific decisions may bemade to achieve the developer's specific goals, such as compliance withsystem related and business related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time consuming but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure. In addition, the compositionused/disclosed herein can also comprise some components other than thosecited. In the summary and detailed description, each numerical valueshould be read once as modified by the term “about” (unless alreadyexpressly so modified), and then read again as not so modified unlessotherwise indicated in context. Also, in the summary and detaileddescription, it should be understood that a concentration range listedor described as being useful, suitable, or the like, is intended thatany concentration within the range, including the end points, is to beconsidered as having been stated. For example, “a range of from 1 to 10”is to be read as indicating each possible number along the continuumbetween about 1 and about 10. Thus, even if specific data points withinthe range, or even no data points within the range, are explicitlyidentified or refer to a few specific points, it is to be understoodthat inventors appreciate and understand that any and all data pointswithin the range are to be considered to have been specified, and thatinventors possessed knowledge of the entire range and all points withinthe range.

FIG. 1 shows one example of a wireline logging system 100 at a wellsite. Such a wireline logging system 100 can be used to implement arapid formation fluid analysis. In this example, a wireline tool 102 islowered into a wellbore 104 that traverses a formation 106 using a cable108 and a winch 110. The wireline tool 102 is lowered down into thewellbore 104 and makes a number of measurements of the adjacentformation 106 at a plurality of sampling locations along the wellbore104. The data from these measurements is communicated through the cable108 to surface equipment 112, which may include a processing system 113for storing and processing the data obtained by the wireline tool 102.The surface equipment 112 includes a truck that supports the wirelinetool 102. In other embodiments, the surface equipment may be located inother locations, such as within a cabin on an off-shore platform.

FIG. 2 shows a more detailed view of the wireline tool 102. The wirelinetool 102 includes a selectively extendable fluid admitting assembly(e.g., probe) 202. This assembly 202 extends into the formation 106 andwithdraws formation fluid from the formation 216 (e.g., samples theformation). The fluid flows through the assembly 202 and into a mainflow line 204 within a housing 206 of the tool 102. A pump module 207 isused to withdraw the formation fluid from the formation 106 and pass thefluid through the flow line 204. The wireline tool 102 may include aselectively extendable tool anchoring member 208 that is arranged topress the probe 202 assembly against the formation 106.

The wireline tool 102 also includes a fluid analyzer module 210 foranalyzing at least a portion of the fluid in the flow line 204. Thisfluid analyzer module 210 is further described below. After the fluidanalysis module 210, the formation fluid may be pumped out of the flowline 204 and into the wellbore 104 through a port 212. Some of theformation fluid may also be passed to a fluid collection module 214 thatincludes chambers for collecting fluid samples and retaining samples ofthe formation fluid for subsequent transport and testing at the surface(e.g., at a testing facility or laboratory).

FIG. 3A shows a more detailed view of a fluid analysis module 210. Asshown in FIG. 3A, the fluid analysis module 210 includes a secondaryflow line 302 (e.g., a channel) that is coupled through a valve 304 tothe main flow line 204. The valve 304 selectively passes a sample offormation fluid into the secondary flow line 302. The secondary flowline 302 also includes a membrane 306 to separate water from theformation fluid sample (e.g., a hydrophobic membrane). Such a membraneis described in U.S. Pat. No. 7,575,681 issued on Aug. 18, 2009 and U.S.Pat. No. 8,262,909 issued on Sep. 11, 2012, each of which is herebyincorporated by reference in its entirety.

In some embodiments, a pump or a piston is used to extract the formationfluid sample from the main flow line 204 and pass the formation fluidthrough the membrane 306. In various embodiments, the membrane 306separates water from the formation fluid sample as the sample is beingextracted from the main flow line 304. Also, although the membrane 306is disposed after the valve 304, it should be appreciated that in someembodiments the membrane 306 is disposed before the valve 304. Moreover,although a single membrane 306 is provided in FIG. 3A, it should beunderstood that some embodiments include multiple membranes.

Once the formation fluid sample passes the membrane 306, the sampleflows into a fluid analyzer 308 that analyzes the sample to determine atleast one property of the fluid sample. The fluid analyzer 308 is inelectronic communication with the surface equipment 112 through, forexample, a telemetry module and the cable 108. Accordingly, the dataproduced by the fluid analyzer 308 can be communicated to the surfacefor further processing by processing system.

The fluid analyzer 308 can include a number of different devices andsystems that analyze the formation fluid sample. For example, in oneembodiment, the fluid analyzer 308 includes a spectrometer that useslight to determine a composition of the formation fluid sample. Thespectrometer can determine an individual fraction of methane (C₁), anindividual fraction of ethane (C₂), a lumped fraction of alkanes withcarbon numbers of three, four, and five (C₃-C₅), and a lumped fractionof alkanes with a carbon number equal to or greater than six (C₆₊). Anexample of such a spectrometer is described in U.S. Pat. No. 4,994,671issued on Feb. 19, 1991 and U.S. Patent Application Publication No.2010/0265492 published on Oct. 21, 2012, each of which is incorporatedherein by reference in its entirety. In some embodiments, the fluidanalyzer 308 includes a gas chromatograph that determines a compositionof the formation fluid. In some embodiments, the gas chromatographdetermines an individual fraction for each alkane within a range ofcarbon numbers from one to 25 (C₁-C₂₅). Examples of such gaschromatographs are described in U.S. Pat. No. 8,028,562 issued on Oct.4, 2011 and U.S. Pat. No. 7,384,453 issued on Jun. 10, 2008, each ofwhich is hereby incorporated by reference in its entirety. The fluidanalyzer 308 may also include a mass spectrometer, a visible absorptionspectrometer, an infrared absorption spectrometer, a fluorescencespectrometer, a resistivity sensor, a pressure sensor, a temperaturesensor, a densitometer, and/or a viscometer. The fluid analyzer 308 mayalso include combinations of such devices and systems. For example, thefluid analysis module 210 may include a spectrometer followed by a gaschromatograph as described in, for example, U.S. Pat. No. 7,637,151issued on Dec. 29, 2009 and U.S. patent application Ser. No. 13/249,535filed on Sep. 30, 2011, each of which is incorporated herein byreference in its entirety.

FIG. 3B shows a fluid analysis module 310 in accordance with anotherembodiment of the present disclosure. In this example, a bypass flowline 301 is coupled to the main flow line 204 through a first valve 305.The first valve 305 selectively passes formation fluid from the mainflow line 204 into the bypass flow line 301. A secondary flow line 307(e.g., a channel) is coupled through a second valve 309 (e.g., anentrance valve) to the bypass flow line 301. The second valve 309selectively passes a sample of formation fluid into the secondary flowline 307. The fluid analysis module 310 includes a membrane 311 toseparate water from the formation fluid sample (e.g., a hydrophobicmembrane). In this embodiment, the membrane 311 is disposed before thesecond valve 309. The fluid analysis module 310 also includes a thirdvalve 313 (e.g., an exit valve) between the secondary flow line 307 andthe bypass flow line 301. The second valve 309 and the third valve 313can be used to isolate the formation fluid sample within the secondaryflow line 307. After analysis, the formation fluid sample can pass tothe bypass flow line 301 through the third valve 313.

In the example of FIG. 3B, the fluid analysis module 310 furtherincludes a spectrometer 315 followed by a densitometer 317 and aviscometer 319. Such an arrangement provides both a chemical compositionfor the fluid sample and physical characteristics for the fluid sample(e.g., density and viscosity). As explained above, other combinations ofdevices and systems that analyze the formation fluid sample are alsopossible.

In FIG. 3B, the fluid analysis module 310 also includes a pressure unit321 for changing the pressure within the fluid sample and a pressuresensor 323 that monitors the pressure of the fluid sample within thesecondary flow channel 307. In some embodiments, the pressure unit 321is a piston that is in communication with the secondary flow line 307and that expands the volume of the fluid sample to decrease the pressureof the sample. As explained above, the second valve 309 and the thirdvalve 313 can be used to isolate the formation fluid sample within thesecondary flow line 307. Also, in some embodiments, the pressure unit321 can be used to extract the formation fluid sample from the bypassflow line 301 by changing the pressure within the secondary flow line307. The pressure sensor 323 is used to monitor the pressure of thefluid sample within the secondary flow line 307. The pressure sensor 323can be a strain gauge or a resonating pressure gauge. By changing thepressure of the fluid sample, the fluid analyzer module 310 can makemeasurements related to phase transitions of the fluid sample (e.g.,bubble point or asphaltene onset pressure measurements). Further detailsof devices and systems that analyze the formation fluid sample are alsoprovided in PCT Application Publication No. WO 2014/158376 A1, which ishereby incorporated herein by reference in its entirety.

Referring to FIG. 1, near the bottom of the wellbore 104, the pressuremay be sufficiently high that the fluid is single-phase. At a givenmid-point (the location of which may vary depending on well properties),the pressure may reach the bubble point when the fluid breaks phase,producing gaseous and liquid phases. While the fluid is transiting fromthe wellbore bottom to the surface, the temperature is monotonicallydecreasing, increasing the fluid viscosity.

Fluids that may be produced from the formation have their temperaturechanged as they are brought to the surface, and hence experience adramatic change in the fluid properties, including but not limited totheir density. In order to accurately calculate the flow rate duringproduction, an accurate knowledge of the density as a function of depthis useful. Along with temperature dependence, the fluid pressure maydrop below the bubble point while in transit. Some example systems 100may obtain a fluid sample from the formation and rapidly vary itstemperature in order to simulate the fluid's passage through the oilwell during the production stage. In some embodiments, the tool 102 maystore a sample extracted from the formation after measurements areperformed. The tool 102 may be raised to a shallower depth and allow thesample within the PVT device to come to equilibrium, after whichadditional measurements may be performed. It should be understood thatalthough the tool 102 in the illustrated examples is a wireline tool,the features of the tool 102 may implemented into any suitable apparatusand may be provided to operate in downhole and/or surface locations.

As an example, a description for measuring density will be discussed,with a comparison of the amount of energy to change the sampletemperature for both mesoscopic and microfluidic approaches. This wouldapply as well to a bubble point measurement where one is interested inthe temperature dependence as well. The present embodiments may becompared to a conventional viscometer that is macroscopic in size and isdirectly immersed in the flow-line which has an inner diameter ofapproximately 5.5 mm. The total amount of fluid to fill the conventionalsensors and the surrounding region volume is on the order of 10milliliters, with an associated heat capacity of, assuming the specificheat of mineral oil, 1.7 Joules/(gram Kelvin), or a heat capacity ofapproximately 20 Joules/Kelvin. Hence, 20 Joules of energy are removedto reduce the temperature by one degree Kelvin. Furthermore, as thesensors are thermally connected to a large metallic assembly on theorder of 1 kilogram (or more), in practice one would reduce thetemperature of this assembly as well. Assuming a specific heat of 0.5Joules/(gram Kelvin) for steel, one would have to remove 500 Joules ofenergy to reduce the temperature of the whole assembly by one degree.This approach using conventional technologies will be referred to asmesoscopic herein.

As a comparison, microfluidic environments of the present disclosure mayuse fluid volumes on the order of ten microliters, which corresponds toaround 10 milligrams of liquid, which has a heat capacity of about 0.02Joules/Kelvin (using the above numbers for the specific heat). Inpractice, one controls the temperature of the microfluidic chamber aswell, which may have a mass on the order of 50 grams, and assuming thisis fabricated from titanium, with a specific heat of 0.5 Joules/(gramKelvin), it would use on the order of 25 Joules of energy to change thetemperature by one degree. Note that this power usage for themicrofluidic approach is 20 times smaller than for mesoscopic approach.Peltier (or thermoelectric) coolers reveals that models with dimensionswith the proper scale exist and are specified to produce heat fluxes onthe order of 1 Joule/second (1 watt), and one may quickly ramp up ordown the temperature of such a device. Hence, a rapid ramping up or downof the temperature of a microfluidic-scale of fluidic volume andassociated chamber is feasible.

As indicated above, during a process of sampling fluid into themicrofluidic system 210, 310 of the tool 102, a fluid may be sampledfrom the formation 106. In some embodiments, a small volume (on theorder of tens of microliters) of fluid will be sampled, filtered, andpassed into the microfluidic system 210, 310. The system 210, 310 may beplaced into a pressure compensation system where during the initialphase of its operation, the pressure is approximately 100 psi lower (orless) than the flowline of the tool in which it will be implemented. Asdiscussed above, the microfluidic system 210, 310 may includemicrofluidic sensors to measure the density, viscosity or any otherphysical properties of the fluid. The microfluidic system 210, 310 mayeither be located downhole or at the surface.

For downhole applications, the fluid evaluation may be motivated by thefact that wellbore temperature changes substantially from the formationto the surface. Fluids that are produced from the formation change theirtemperature accordingly and hence experience a dramatic change in theirproperties, including but not limited to their density. In order toaccurately calculate the flow rate during production one shouldaccurately know the density as a function of depth. This is furthercomplicated by the fact that the fluid may drop below the bubble pointwhile in transit. Hence, a system may be selected that can obtain afluid sample from the formation and rapidly vary its temperature inorder to simulate its passage through the wellbore during the productionstage.

Generally, examples disclosed herein relate to collecting a fluid from awellbore, a fracture in a formation, a body of water or oil or mixtureof materials, or other void in a subterranean formation that is largeenough from which to collect a sample. The fluid may contain solidparticles such as sand, salt crystals, proppant, solid acids, solid orviscous hydrocarbon, viscosity modifiers, weighing agents, completionsresidue, or drilling debris. The fluid may contain water, salt water,hydrocarbons, drilling mud, emulsions, fracturing fluid, viscosifiers,surfactants, acids, bases, or dissolved gases such as natural gas,carbon dioxide, or nitrogen.

Systems for analyzing these fluids may be located in various locationsor environments, including, but not limited to, tools for downhole use,permanent downhole installations, or any surface system that willundergo some combination of elevated pressures, temperatures, and/orshock and vibration. In some embodiments, temperatures may be as high asabout 175° C. or about 250° C. with pressures as high as about 25,000psi.

In general, energy added to a fluid at pressures near the bubble pointto overcome the nucleation barrier associated with bubble production.Thus, energy may be added to a fluid thermally through the process ofthermal nucleation. The quantity of bubbles produced at thethermodynamic bubble point via thermal nucleation is sufficiently smallthat their presence is detectable near the place of thermal nucleationin a phase transition cell and not in other components in themeasurement system. However, upon further depressurization of thesystem, the supersaturation becomes large enough that bubble nucleationspontaneously occurs throughout the measurement system. In one or moreembodiments, a fluid sample may be depressurized at a rate such thatbubble detection may occur in a phase transition cell alone, or may besufficiently high enough to be detected throughout the overall system.

During depressurization of a sample, the density, viscosity, opticaltransmission through the phase transition cell, and sample pressure maybe simultaneously measured. Depressurization starts at a pressure abovethe saturation pressure and takes place with a constant change in systemvolume, a constant change in system pressure, or discreet pressurechanges.

Collecting and analyzing a small sample with equipment with a smallinterior volume allows for precise control and rigorous observation whenthe equipment is appropriately tailored for measurement. At elevatedtemperatures and pressures, the equipment may also be configured foreffective operation over a wide temperature range and at high pressures.Selecting a small size for the equipment is advantageous for ruggedoperation because the heat transfer and pressure control dynamics of asmaller volume of fluid are easier to control then those of largevolumes of liquids. That is, a system with a small exterior volume maybe selected for use in a modular oil field services device for usewithin a wellbore. A small total interior volume can also allow cleaningand sample exchange to occur more quickly than in systems with largervolumes, larger surface areas, and larger amounts of dead spaces.Cleaning and sample exchange are processes that may influence thereliability of the microfluidic system 210, 310. That is, the smallervolume uses less fluid for observation, but also can provide resultsthat are more likely to be accurate.

The minimum production pressure of the reservoir may be determined bymeasuring the saturation pressure of a representative reservoir fluidsample at the reservoir temperature. In a surface measurement, thereservoir phase envelope may be obtained by measuring the saturationpressure (bubble point or dewpoint pressures) of the sample using atraditional PVT view cell over a range of temperatures. Saturationpressure can be either the bubble or dewpoint of the fluid, dependingupon the fluid type. At each temperature, the pressure of a reservoirsample is lowered while the sample is agitated with a mixer. This isdone in a view cell until bubbles or condensate droplets are opticallyobserved and is known as a Constant Composition Expansion (CCE). The PVTview cell volume is on the order of tens to hundreds of milliliters,thus using a large volume of reservoir sample to be collected foranalysis. This sample can be consumed or altered during PVTmeasurements. A similar volume may be used for each additionalmeasurement, such as density and viscosity, in a surface laboratory.Thus, the small volume of fluid used by microfluidic sensors of thepresent disclosure (approximately 1 milliliter total for measurementsdescribed herein) to make measurements may be highly advantageous.

In one or more embodiments, an optical phase transition cell may beincluded in a microfluidic PVT tool. It may be positioned in the fluidpath line to subject the fluid to optical interrogation to determine thephase change properties and its optical properties. U.S. patentapplication Ser. No. 13/403,989, filed on Feb. 24, 2012 and UnitedStates Patent Application Publication Number 2010/0265492, published onOct. 21, 2010 describe embodiments of a phase transition cell and itsoperation. Each of these applications is incorporated herein byreference in its entirety. The pressure-volume-temperature phasetransition cell may contain as little as 300 μl, or less, of fluid. Thephase transition cell detects the dew point or bubble point phase changeto identify the saturation pressure while simultaneously nucleating theminority phase.

The phase transition cell may provide thermal nucleation whichfacilitates an accurate saturation pressure measurement with a rapiddepressurization rate of from about 10 to about 200 psi/second. As such,a saturation pressure measurement (including depressurization fromreservoir pressure to saturation pressure) may take place in less than10 minutes, as compared to the saturation pressure measurement viastandard techniques in a surface laboratory, wherein the samemeasurement may take several hours.

Some embodiments may include a view cell to measure the reservoirasphaltene onset pressure (AOP) as well as the saturation pressures.Hence, the phase transition cell becomes a configuration to facilitatethe measurement of many types of phase transitions during a CCE.

In one or more embodiments, the densitometer 317, viscometer 319, apressure gauge and/or a method to control the sample pressure with aphase transition cell may be integrated so that most sensors and controlelements operate simultaneously to fully characterize a live fluid'ssaturation pressure. In some embodiments, each individual sensor itself(e.g., densitometer 317 or viscometer 319) has an internal volume of nomore than 20 microliters (approximately 2 drops of liquid) and byconnecting each in series, the total volume (500 microliters) to chargethe system with live oil before each measurement may be minimized. Insome embodiments, the fluid has a total fluid volume of about 1.0 mL orless. In other embodiments, the fluid has a total fluid volume of about0.5 mL or less.

This configuration is substantially different than a traditionalPressure-Volume-Temperature (PVT) apparatus, but provides similarinformation while reducing the amount of fluid consumed for measurement.FIG. 3A is a schematic of one embodiment of a PVT apparatus for usedownhole. In some embodiments, the PVT apparatus may be included intoanother measurement tool or may be standalone on a drill string or wireline.

The system's 210, 310 small dead volume (less than 0.5 mL) facilitatespressure control and sample exchange. In some embodiments, thedepressurization or pressurization rate of the fluid is less than 200psi/second. In some embodiments, the fluid is circulated through thesystem at a volumetric rate of no more than 1 ml/sec.

As mentioned above, the tool of the present disclosure may include adensitometer 317 (or analogous densitometer of fluid analyzer 308) tomeasure fluid density which, in some examples, may be used to calculatecompressibility. The fluid compressibility, k, can be calculated byprecisely measuring the fluid density while varying the pressure. Thecompressibility can be defined as the relative change in fluid densitywith the change in pressure as in the following equation:

$\begin{matrix}{{k\lbrack p\rbrack} = {\frac{1}{\rho}\frac{\partial\rho}{\partial P}}} & (1)\end{matrix}$

FIGS. 4A to 5H show components of the densitometer 317. It should beunderstood that, although the example device is a configured to functionas a densitometer, any suitable fluid analysis system may implementfeatures analogous to those described in connection with thedensitometer 317. For example, a microfluidic coriolis force meter mayimplement analogous isolation, electrical, structural, and/orvibrational features to those described in connection with densitometer317.

FIGS. 4A and 4B show a vibrating tube densitometer module 2000 of thedensitometer 317 with integrated electrical isolation components. AU-shaped thin vibrating tube element 2002 functions as the vibratingelement of the vibrating tube densitometer module 2000. A proximal endportion of the vibrating tube element 2002 is supported at a body block2010, leaving the remaining portion of the vibrating tube element 2002cantilevered to allow for the vibration utilized in the operation of thedensitometer 2000. The proximal portion of the tube element 2002, whichincludes two open tube ends corresponding to two respective legs 2003,is hermetically sealed with respect to the body block 2010 to preventsample fluids from leaking as they pass into and out of the tube element2002.

Referring to the cross-sectional views of FIGS. 4C and 4D an electricalinsulator 2015 couples the proximal end of each of the two legs of thevibrating tube element 2002 to the body block 2010. This coupling 2015mechanically supports the vibrating tube element 2002 and simultaneouslyprovides electrical insulation to prevent electrical currents frompassing from the body block 2010 or other portion of the densitometer2000 to the vibrating tube element 2002 and vice-versa, therebyelectrically isolating the vibrating tube element 2002 from the bodyblock 2010. This prevents electrical noise present in components such asconductive fluid delivery tubes and the body block 2010 from interferingwith the electrical signals utilized with the vibrating tube element2002 during density measurements.

As illustrated in FIG. 4D, the electrical insulator 2015 extends alongthe proximal end portion of the leg 2003 of the vibrating tube element2002. The electrical insulator 2015 is formed of glass. In someexamples, the electrical insulator 2015 is formed by glass frit bondingusing doped glass powder. The doped glass powder has a low meltingtemperature (e.g., less than 450° C.) that will allow the doped glasspowder to melt while avoiding melting of the body block 2010. Suchpowders may be obtained commercial from, for example, Asahi Glass Co.,LTD of Tokyo, Japan.

Although in some examples, the electrical insulator 2015 is a singlemonolithic component, the electrical insulator 2015 shown in FIGS. 4Cand 4D is formed of two components. In particular, the insulator 2015 isformed of a doped glass body 2016 and a base body 2040. It should beunderstood that the features corresponding to a cross section throughthe second leg 2003 are the same as the features described in connectionwith the cross section through the first leg 2003 illustrated in FIGS.4C and 4D, although in other examples, the features may differ betweenthe two sides.

The doped glass powder is formed into a near-shape glass bead bycompression molding. This near-shape bead is then placed in the positionin the block 2010 where it is to provide an electrically insulativehermetic seal. In the illustrated example, the doped glass bead isplaced into a channel 2011 in the block 2010 and corresponds to thegeneral shape and position as the insulator 2015. After the bead isplaced in the channel 2011, the vibrating tube element 2002 is insertedinto the channel 2011 and into the bead. The structure is then heated tothe melting point of the doped glass bead. During the heating andsubsequent cooling, the doped glass will bond to the metal and becamesolid, thereby securing the tube 2002 in place relative to the block2010.

Referring to the example of FIG. 4D, when the doped glass is in a liquidor non-rigid state during the melting process, the vibrating tubeelement 2002 is maintained in its position spaced apart from the annularchannel wall 2011 by the base bodies 2040 which function as jigs,receiving the respective ends of the legs 2003. The base bodies 2040 inthe illustrated example are formed of an electrically insulativematerial (e.g., glass or ceramic) that has a melting temperaturesubstantially higher than the melting temperature of the doped glassutilized to form the doped glass body 2016. As such, when thedensitometer module 2000 is heated to melt the doped glass to form theinsulator doped glass body 2016, the base bodies 2040 remain solid,thereby retaining adequate structure to maintain the insulator dopedglass body in its position spaced apart from the channel 2011 of theblock 2010 until the doped glass has cooled and solidified to producethe hermitically sealed solid insulator structure 2015. The base body2040 may also be utilized to block potential flow of the melted dopedglass during the heating process.

FIGS. 5A and 5B show a densitometer module 3000 that is analogous to thedensitometer module 2000 except to the extent described otherwise.

The densitometer module 3000 differs in the structure of the base block3010 and the insulator structure. Referring to the exploded view of FIG.5B and the cross-sectional views of FIGS. 5C and 5D, the channel 3011has an enlarged section 3012 with a diameter that is larger than theremainder of the channel 3011. This enlarged section 3012 receives acorresponding enlarged portion 3017 of the doped glass body 3016.

Further, in addition to the base body 3040 and the doped glass body3016, the electrically insulating coupling 3015 further includes a capbody 3045, which functions as a second jig disposed at the end of thedoped glass body 3016 opposite the base body 3040. This two jigconfiguration—i.e., the base body 3040 and the cap body 3045—serve tostably support the leg 3003 of the vibrating tube element 3002 duringthe melting of the doped glass, and may also be utilized to resist flowof the liquefied or non-solid doped glass from its intended positionduring the heating process.

In the illustrated example, the cap body 3045 further receives andsupports a mass block 3048, which is coupled to the respective leg 3003of the vibrating tube element 3002. The mass block 3048 may be securedto the leg 3003 via the adhesion of the doped glass of the doped glassbody 3016 and/or any other suitable coupling mechanism. In someexamples, the mass block 3048 is present to provide additionalvibrational isolation of the vibrating tube 3002 to improve performanceduring operation of the vibrating tube densitometer 3000 to measurefluid density.

In some examples, the presence of the mass block 3048, in addition tothe rigid connection of the mass block 3048 to the vibrating tubeelement 3002, causes a standing wave node location at the location ofthe mass block 3048 during the vibration of the vibrating tube element3002. In this regard, the mass of the block 3048 coupled with the factthat its location corresponds to the vibrational node allows forelectrical connections be made without altering the vibrationalproperties of the vibrating tube element 3002. For example, theelectrical connections may be made directly to the electricallyconductive mass blocks 3048. Since the mass blocks 3048 are electricallycoupled to the vibrating tube element 3002, applying the electricalleads to the mass blocks 3048 provides a mechanism to apply anexcitation current and/or measure vibrational response without havingthe physical electrical connection adversely impact the performance ofthe device. In particular, the for example, this structure allows forconnecting the electrical leads without altering the resonance of thetube 3002.

As with the base bodies 2040 described above, the base bodies 3040 andthe cap bodies 3045 in the illustrated example are formed of anelectrically insulative material (e.g., glass or ceramic) that has amelting temperature substantially higher than the melting temperature ofthe doped glass utilized to form the doped glass body 3016. As such,when the densitometer 3000 is heated to melt the doped glass to form thedoped glass body 3016, the cap bodies 3045 remain solid, therebyretaining adequate structure to maintain the insulator 2015 in itsposition spaced apart from the channel 3011 of the block 2010 until thedoped glass has cooled and solidified to produce the hermitically sealedsolid insulator structure 2015. It should be understood that the variousinstances of the base bodies 2040, 3040 and cap bodies 3045 in any givenexample may be formed of the same or different materials relative toeach other.

FIG. 5E shows a densitometer subassembly 3500 that includes thevibrating tube densitometer module 3000. The subassembly 3500 furtherincludes high-pressure sealed tube fittings 3155 that mate withreceptacles 3050, which are visible in FIG. 5C, to couple a metalflowline to the sensor module 3000 in order to deliver sample fluids toand away from the vibrating tube element 3002 for density measurements.Because of the insulating coupling 3015, any electrical noise that maybe present in the flowline or other conductive structures is isolatedfrom the vibrating tube element 3002 to prevent such noise frominterfering with the density measurement during operation of thedensitometer. At the same time, the insulating coupling 3015 maintains ahermetic seal between the flowline and the vibrating tube 3002 underoperating conditions of the densitometer. The same features apply withregard to the insulating coupling 2015.

The densitometer subassembly 3500 further includes a magnet unit 3100that includes a mounting bracket 3105 having mounting flanges 3110. Themounting flanges 3110 include recesses 3112 to receive alignment pins,and holes 3114 to receive fasteners 3610 to locate and secure the magnetunit 3100 to a base chassis 3605, as shown in further detail inconnection with FIG. 5F. Similarly, the base block 3010 includesrecesses 3013 to receive locating pins 3615, and a hole 3014 to receivea fastener 3611 to locate and secure the densitometer module 3000 to thebase chassis 3605. Although various fasteners and locating devices maybe described herein, it should be understood that any suitable assemblyand/or manufacturing methods may be employed, and the present disclosureis in no way limited to the specific examples shown and described.

The magnet unit 3100 further includes a pair of magnets 3150 disposed onopposite sides of the vibrating tube element 3002 and adjacent torespective legs 3003 of the vibrating tube element 3002. Magnets 3150are oriented in the same polarized direction. As such, these two magnets3150 are magnetically coupled in series. The magnets 3150 in theillustrated example are permanent magnets that are hightemperature-resistant.

There is also a yoke 3160 disposed between the two legs 3003 of thevibrating tube element 3002. The yoke acts to optimize the magneticfield of the magnets 3150 acting on the vibrating tube 3002. The yoke3160 and the mounting bracket 3105 are formed of a soft magneticmaterial such as a ferrous magnetic material

The two magnets 3150, the yoke 3160, the mounting bracket 3105, and twogaps 3153 form a magnetic circuit in the illustrated example. The gaps3153 may be filled with air or any other suitable medium and aredisposed between the yoke 3160 and a respective magnet 3150 foraccommodating the legs 3003 of the vibrating tube 3002.

Magnetic flux travels through the magnetic mounting bracket 3105 to themagnet 3150 and through gap 3153 resulting in a closed-loop magneticcircuit. In this regard, the element 3105 is not only a mounting bracketbut also a magnetic flux path to enhance permeance of the magneticcircuit.

The magnets 3150 and the yoke 3160 are mounted to a block 3170 which isattached to the mounting bracket 3105. The block 3170 acts to secure andlocate the magnets 3150 and yoke 3160 relative to each other and, as aresult of the various components being mounted to the base chassis 3605as shown in FIG. 5F, relative to the vibrating tube element 3002. Thisspacing and locating allows the magnets 3150 and yoke 3160 to act on thevibrating tube 3002 without coming into contact with the tube 3002 as itvibrates during density measurements. It should be understood thatalthough an example of a magnet configuration is provided in connectionwith FIG. 5E, other magnet configurations may be provided. For example,for different resonances, different magnet positioning and arrangementmay be provided. Some examples do not employ a yoke. Some examplesinclude a single magnet or more than two magnets.

FIG. 5F shows a densitometer assembly 3600 that incorporates thesubassembly 3500. In particular, the subassembly 3500 is mounted to thebase chassis 3605 via fasteners 3610 and 3600 and the locating pins asdiscussed above. The assembly 3600 further includes a sensor front endcircuit board 3620. The front end circuit board 3620 is mounted to thebase chassis 3605 via fasteners 3625, and the base chassis 3605 isattached to a base tool via fasteners 3630. As with the other fasteners3610 and 3611 described above, the fasteners 3625 and 3630 may be boltsor any other suitable fasteners.

The tubing 2002, 3002 may have an outer diameter of 1 mm or less in somenon-limiting examples. The tubing 2002 may be made of stainless steel,Hastelloy, medical grade tubing, etc. In some examples, the tubing 2002and/or other metallic components may be made of spring metal such asSPRON, developed by Seiko Instruments Inc.

The electrical isolation structures illustrated, for example, in FIGS.4D and 5D function to fluidically and hydraulically connect the metaltubes 2002 and 3002 while maintaining electrical isolation of the tubes2002 and 3002 with respect to the inlet tubes and other conductivestructures external to the tubes 2002 and 2003.

In some examples, the block 2010, 3010 is metal (e.g., aluminum orstainless steel), although the block may be formed of any other suitablematerial.

Referring again to FIG. 5E, the vibrating tube element 3002 mounted inthe body block 3010 and wrapped about a yoke 3160 and between magnets3150 such as, for example, SmCo permanent magnets, wherein analternating current is driven through the tube element 3002 and theresulting Lorentz force provides actuation to drive the tube 3002 in atorsional mode and the resulting electromagnetic field (EMF) (Faraday'slaw) is proportional to the tube velocity.

It is noted that motion may be monitored by measuring the small EMFvoltage that develops due to Faraday's law. Example embodiments of thedensitometer are operable to high pressures up to 15,000 psi or more andhigh temperatures up to 150° C. or more for determining measurements ina tube having an outer diameter approximate 1/32″ along with a fluidsampling volume of less than 20 microliters. It is noted thattemperatures in some oilfield applications may reach 150° C. (it isnoted the temperatures could be as high as 350° C.) along with pressuresof 15,000 psi (it is also noted the pressures could be as high as 35,000psi). Further, the diameter of the tube can be greater or less and thefluid sampling volume may be up to, for example, 1000 micro-liters.Further still, the tubes used in this densitometer configuration. bynon-limiting example are made of stainless steel or other relatedmaterials having similar properties. However, other types of metals maybe used (for example, titanium, nickel and related alloys). It isfurther noted that the above-described glass insulator configurationsare also able to withstand the aforementioned pressure and temperatureconditions, such as may be found, for example, downhole during open-holeoperations.

In the illustrated example, each leg 2003, 3003 of the tube 2002, 3002is of approximately length 4.5 cm. The end of the tube 2002, 3002 may bebent into a half circle of an approximate diameter of 1 cm so as tocreate an approximate total internal volume of approximately 20 μl (asnote above the total internal volume may be approximately up to 1000 μl.However, alternative shapes and dimensions for the tube may be provided,such as a straight tube or a tube with differing bends. The body block2010, 3010 may be secured in the downhole housing by any suitablefastening mechanism (e.g., screws, adhesive, soldering, welding,brazing, etc.) and in some examples electrically isolated from thedownhole housing.

A typical high pressure fluidic system connects a metal flowline to theelectrical ground plane, thereby introducing stray impedances whichwould alter if not completely ruin the signal used here to measure fluiddensity. Thus, the glass insulators 2015, 3015 are provided toelectrically isolate the two coupled tubes, along with being capable ofoperating in high shock and high temperature device conditions. Incontrast with some other potential solutions, the electrical isolationstructure of, e.g., FIGS. 4D and 5D provide electrical isolation withoutadding an unacceptable amount of dead volume. Since these sensors areconsidered to be microfluidic, the addition of a significant amount ofdead volume (e.g. greater than a few, e.g., 3, microliters) would renderthe sensor inoperable in some intended microfluidic applications, orwould require greater flushing volume.

Electrical connections to the tube 3002 may be provided in the form of,referring to FIG. 5G, wires 3640, may be soldered or otherwise attachedto be in electrical communication with respective legs of the tube 3002.As indicated above, the connection of the electrical leads at the massblocks 3048 in the illustrated example allows for an electricalconnection that does not mechanically affect the vibrational propertiesof the tube 3002 by, for example, altering the relevant resonancefrequency of the tube 3002 in the absence of such connection.

An electrical control system 3650, which may be, for example, front endcircuit board 3620, is connected to the electrical connections 3640 toprovide the voltage and current across the electrical leads andcorresponding legs of the tube element 3002 to induce the aforementionedvibrations. The control system 3650 is also configured to measure theresulting EMF, which is in turn used to determine the density of thefluid present in the vibrating tube element 3002. In this regard, theEMF reflects the resonant frequency of the tube 3002 together with thesample fluid inside the tube 3002. Since this frequency varies as afunction of the density of the sample fluid in the tube 3002, itprovides a mechanism by which to measure the density of the fluid. Itshould be understood that instead of a single unit 3650 that drives thecurrent and senses the EMF, separate systems may be provided. Moreover,alternatively or additionally, the frequency of the vibrating tube 3002may be measured by any other suitable mechanism, e.g., using opticaldetection. FIG. 5H shows an example of an optical detection system 3700including a light source 3705 and a light sensor 3710. In thisarrangement, the signal generated from the light sensor 3710 varies as afunction of the frequency at which the tube 3002 vibrates. Accordingly,the control system 3650 can process the signal to determine thefrequency.

It is further noted that in addition to the vibration, the controlsystem of the illustrated example factors in temperature and pressure indetermining the density of the fluid.

Additional details of the operation of the densitometer configurations2000 and 3500 may be found in U.S. Patent Application Publication No.2010/0268469, which is incorporated herein by reference in its entiretyand provides an analogous densitometer structure and function, butwithout, for example, the glass isolator configuration of the presentapplication.

Further details of using the PVT apparatus in conjunction with awellbore tool and methods for implementing the PVT apparatus aredescribed in U.S. Patent Application Publication No. 2014/0260586 andPCT International Publication No. WO 2014/158376, each of which isincorporated herein by reference in its entirety.

The methods and processes described above such as, for example,operation of valves and pistons and the performance of the variousdescribed fluid analyses, may be performed by a processing system. Theprocessing system may correspond at least in part to element 3650described above. The term “processing system” should not be construed tolimit the embodiments disclosed herein to any particular device type orsystem. The processing system may include a single processor, multipleprocessors, or a computer system. Where the processing system includesmultiple processors, the multiple processors may be disposed on a singledevice or on different devices at the same or remote locations relativeto each other. The processor or processors may include one or morecomputer processors (e.g., a microprocessor, microcontroller, digitalsignal processor, or general purpose computer) for executing any of themethods and processes described above. The computer system may furtherinclude a memory such as a semiconductor memory device (e.g., a RAM,ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device(e.g., a diskette or fixed disk), an optical memory device (e.g., aCD-ROM), a PC card (e.g., PCMCIA card), or other memory device.

The methods and processes described above may be implemented as computerprogram logic for use with the computer processor. The computerprocessor may be for example, part of a system such as system 100described above. The computer program logic may be embodied in variousforms, including a source code form or a computer executable form.Source code may include a series of computer program instructions in avariety of programming languages (e.g., an object code, an assemblylanguage, or a high-level language such as C, C++, Matlab, JAVA or otherlanguage or environment). Such computer instructions can be stored in anon-transitory computer readable medium (e.g., memory) and executed bythe computer processor. The computer instructions may be distributed inany form as a removable storage medium with accompanying printed orelectronic documentation (e.g., shrink wrapped software), preloaded witha computer system (e.g., on system ROM or fixed disk), or distributedfrom a server or electronic bulletin board over a communication system(e.g., the Internet or World Wide Web).

Alternatively or additionally, the processing system may includediscrete electronic components coupled to a printed circuit board,integrated circuitry (e.g., Application Specific Integrated Circuits(ASIC)), and/or programmable logic devices (e.g., a Field ProgrammableGate Arrays (FPGA)). Any of the methods and processes described abovecan be implemented using such logic devices.

Any of the methods and processes described above can be implemented ascomputer program logic for use with the computer processor. The computerprogram logic may be embodied in various forms, including a source codeform or a computer executable form. Source code may include a series ofcomputer program instructions in a variety of programming languages(e.g., an object code, an assembly language or a high-level languagesuch as C, C++ or JAVA). Such computer instructions can be stored in anon-transitory computer readable medium (e.g., memory) and executed bythe computer processor. The computer instructions may be distributed inany form as a removable storage medium with accompanying printed orelectronic documentation (e.g., shrink wrapped software), preloaded witha computer system (e.g., on system ROM or fixed disk), or distributedfrom a server or electronic bulletin board over a communication system(e.g., the Internet or World Wide Web).

To the extent used in this description and in the claims, a recitationin the general form of “at least one of [a] and [b]” should be construedas disjunctive. For example, a recitation of “at least one of [a], [b],and [c]” would include [a] alone, [b] alone, [c] alone, or anycombination of [a], [b], and [c].

Although a few example embodiments have been described in detail above,those skilled in the art will readily appreciate that many modificationsare possible in the example embodiments without materially departingfrom embodiments disclosed herein. Accordingly, all such modificationsare intended to be included within the scope of this disclosure.

What is claimed is:
 1. A device for measuring a property of a fluid sample, the device comprising: a tube configured to receive the fluid sample; a base block supporting the tube; a magnet configured to apply a magnetic field to the tube; an excitation source configured to generate vibration of the tube when the fluid sample is received in the tube by circulation of an electrical current along a portion of the tube and interaction of the electrical current to at least one magnetic field produced by the magnet; a vibration sensor configured to measure a signal corresponding to a vibration frequency of the tube; an electrical isolator comprised of glass and separate and distinct from the base block, wherein the tube is hermetically sealed to the base block via the electrical isolator and electrically isolated from the base block via the electrical isolator, and wherein the base block has an internal channel and the electrical isolator is disposed in the internal channel of the base block; and a mass block that is electrically coupled to the tube to provide an electrical connection between the excitation source and the tube, wherein the mass block is rigidly coupled to the tube such that the mass block provides a standing wave vibrational node of the tube when the excitation source generates the vibration of the tube, and wherein the mass block is electrically isolated from the base block by the electrical isolator.
 2. The device of claim 1, further comprising an electrical lead attached to the mass block and configured to convey an excitation current from the excitation source to the tube via the mass block.
 3. The device of claim 2, further comprising: a second electrical isolator comprised of glass and separate and distinct from the base block, wherein first and second ends of the tube are hermetically sealed to the base block via the electrical isolator and the second electrical isolator and electrically isolated from the base block via the electrical isolator and the second electrical isolator; a second mass block that is electrically coupled to the tube to provide a second electrical connection between the excitation source and the tube, wherein the second mass block is rigidly coupled to the tube such that the second mass block provides a standing wave vibrational node of the tube when the excitation source generates the vibration of the tube, wherein the second mass block is isolated from the base block by the second electrical isolator; and a second electrical lead attached to the second mass block, wherein the electrical lead, the mass block, the tube, the second mass block, and the second electrical lead form an electrical circuit via which the excitation source is configured to apply the excitation current across the tube.
 4. The device of claim 1, wherein the device is configured to measure a density of the fluid sample.
 5. The device of claim 1, wherein the device is configured to measure a flow rate of the fluid sample.
 6. The device of claim 1, wherein the excitation source and the vibration sensor are a single component.
 7. The device of claim 1, wherein the electrical isolator comprised of two glass elements, each corresponding to a respective end of the tube.
 8. The device of claim 1, wherein the glass is a doped glass.
 9. The device of claim 8, wherein the doped glass has a melting point that is lower than respective melting points of the base block and the tube.
 10. The device of claim 9, further comprising a jig configured to maintain a position of the tube relative to the base block when the doped glass is melted.
 11. The device of claim 10, wherein the jig is comprised of a glass material having a melting point that is higher than the melting point of the doped glass.
 12. The device of claim 1, further comprising a processor configured to determine a resonant frequency of the tube based on the signal measured by the vibration sensor.
 13. The device of claim 1, wherein the device is configured to operate downhole in a wellbore.
 14. The device of claim 1, further comprising a yoke configured to alter the magnetic field produced by the magnet when the magnetic field is applied to the tube.
 15. The device of claim 14, wherein the magnet is comprised of two separate magnetic elements and the yoke is disposed between the two separate magnetic elements.
 16. The device of claim 14, wherein the tube is a U-shaped element having two legs, the yoke is disposed between the two legs.
 17. The device of claim 16, wherein the magnet is comprised of two separate magnetic elements, the yoke is disposed between the two separate magnetic elements, and each leg of the U-shaped element is disposed between the yoke and a respective one of the magnetic elements.
 18. The device of claim 1, wherein the electrical isolator is disposed between the mass block and the base block.
 19. The device of claim 1, wherein the electrical isolator includes a recess for receiving the mass block.
 20. The device of claim 1, wherein the electrical isolator and the mass block both include respective passageways through which the tube extends.
 21. A system for characterizing a fluid, comprising: a phase transition cell configured to receive the fluid; a piston configured to control pressure of the fluid; a pressure gauge configured to measure the pressure of the fluid and to provide information to control the piston; and a fluid analyzer configured to measure a property of the fluid, the analyzer comprising a tube configured to receive a fluid sample, a base block supporting the tube, a magnet, an excitation source configured to generate vibration of the tube when the fluid sample is received in the tube by circulation of an electrical current along a portion of the tube and interaction of the electrical current to at least one magnetic field produced by the magnet, a vibration sensor configured to measure a signal corresponding to vibrations of the tube, an electrical isolator comprised of glass and separate and distinct from the base block, wherein the tube is mounted to the base block via the electrical isolator and electrically isolated from the base block via the electrical isolator, and wherein the base block has an internal channel and the electrical isolator is disposed in the internal channel of the base block, and a mass block that is electrically coupled to the tube to provide an electrical connection between the excitation source and the tube, wherein the mass block is rigidly coupled to the tube such that the mass block provides a standing wave vibrational node of the tube when the excitation source generates the vibration of the tube, and wherein the mass block is electrically isolated from the base block by the electrical isolator.
 22. The device of claim 21, wherein the device is configured to operate downhole in a wellbore.
 23. The device of claim 21, wherein the fluid analyzer is a vibrating tube densitometer.
 24. A device for measuring a property of a fluid sample, the device comprising: a tube having first and second ends, the tube configured to receive the fluid sample; a base block supporting the tube; a magnet configured to apply a magnetic field to the tube; an excitation source configured to generate vibration of the tube when the fluid sample is received in the tube by circulation of an electrical current along a portion of the tube and interaction of the electrical current to at least one magnetic field produced by the magnet; a vibration sensor configured to measure a signal corresponding to a vibration frequency of the tube; two electrical isolators comprised of glass and separate and distinct from the base block, wherein the first and second ends of the tube are hermetically sealed to the base block via the two electrical isolators and electrically isolated from the base block via the two electrical isolators, and wherein the base block has two internal channels and the two electrical isolators are disposed in the two internal channels of the base block; and two mass blocks that are electrically coupled to the tube to provide electrical connections between the excitation source and the tube, wherein the two mass blocks are rigidly coupled to the tube such that the two mass blocks each provide a standing wave vibrational node of the tube when the excitation source generates the vibration of the tube, and wherein the two mass blocks are electrically isolated from the base block by the two electrical isolators. 